1. Field of the Invention
This invention relates to the assessment of the condition of fruit and vegetables.
2. Description of the Prior Art
When fruit and vegetables are harvested it is often the case that the crop is of varying degrees of ripeness. Often no special steps are taken to separate the crop according to the extent of ripeness. As a result fruit and vegetables that are sent for storage may already be ripe and ready for consumption and unripe fruit and vegetables may be offered for sale. It is, therefore, a matter of chance to some extent whether the fruit and vegetables at the point of sale are in the optimum condition of ripeness for consumption. Ripe fruit and vegetables put into cold storage tend to be over-ripe by the time they have been removed from the storage and transported to the retail outlet. Frequently such produce cannot even be sold at all and has to be thrown away. This is a serious problem. It has been estimated that a very large quantity of fruit and vegetables is wasted because, being over-ripe when it arrives at the point of sale, it is unsaleable.
Problems of a different kind arise with under-ripe produce. This may look quite acceptable when displayed at the point of sale. However, when a purchaser consumes unripe fruit or vegetables a strongly negative impression is received. This may have the effect of persuading the purchaser not to buy such produce from the same retail outlet again.
EP-A-0 439 405 discloses an apparatus in which a punch is driven towards a fruit at constant speed until it contacts the fruit. The apparatus allows the measurement of the diameter of the fruit and the weight and, if the punch penetrates or crushes the fruit, the ripeness can be measured.
According to the invention there is provided an assembly for measuring the condition of fruit and vegetables comprising plunger means, and a passive sensor carried by the plunger means, said plunger means being adapted to bring the passive sensor into contact with, or adjacent to, an item of fruit or vegetables whereby the sensor reacts to a property of said fruit item or vegetables to produce a signal related to that property characterized in that the plunger means comprises a resilient bellows assembly which is capable of expansion under the action of pressurized air and retraction by application of a vacuum, the expansion and retraction of the bellows being timed so as to coincide with the presentation of a fruit or vegetable item for assessment.
The invention is particularly suitable for installation in a packhouse where the fruit or vegetables are brought for grading after they have been harvested. Items of fruit travelling on a conveyor can be individually examined using the apparatus of the invention. The results of the examination, that is to say, the signal from the passive sensor, provide an indication of the ripeness or maturity of the fruit item or vegetable and thus the fruit or vegetables can be sorted according to the degree of ripeness or maturity. Under-ripe produce can be held back and sent to storage whereas more mature produce can be forwarded for immediate sale. There can be as many grades between these extremes as may be desired.
The property that the passive sensor is to read can be any property which is indicative of the condition of a fruit or vegetable item. Many of these are well known. The properties that are particularly preferred for measurement by the present invention include surface gas detection, chlorophyll fluorescence, visible and Near Infra Red spectrometry, charge transfer, delayed light emission and resonance.
It is well known that as fruit and vegetables ripen there is emission of gas from their surface. This gas emission is indicative of the condition of the produce. The passive sensor can be adapted to take a sample of this surface gas emission from a fruit or vegetable item, which sample can then be analyzed to provide a signal indicative of the condition of the produce.
It is also known that chlorophyll fluorescence declines as ripening advances. In order to make use of that phenomenon the passive sensor may be an optical device such as one or more optic fibers. Alternatively a passive sensor may be used to scan produce by Near Infra Red spectrometry. This, as is known, gives an indication of the soluble solids in the produce. The major part of the soluble solids in most cases will be sugars so this measurement gives an indication of the ripeness or maturity of the produce. It is also known that Near Infra Red spectrometry can give an indication of material structure and therefore this information can also be used to give an indication of the ripeness or maturity of the produce.
It is further known that different ripeness of produce leads to the produce having different capacitance. Therefore an indication of the ripeness of the product can be provided by the capacitance of the produce. The capacitance of the produce can be measured by having the sensor comprise a charged capacitor, the presence of produce adjacent to which causes a variation in the charge stored in the capacitor, the amount of which is dependent on the capacitance of the produce and hence its ripeness. The change in stored charge on the capacitor can be detected by a second capacitor in what is known as xe2x80x9ccharge transfer sensingxe2x80x9d.